fix console attribute in lxc template

commit 4aa5da278f49c889d43191f82ff42d3a95266d62 moves `Console` from Command to
ProcessConfig, but missed the change in lxc_template. Therefore creating a
container with tty using lxc driver with fail with error

template: lxc:60:20: executing "lxc" at <.Console>: Console is not a field of
struct type struct { *execdriver.Command; AppArmor bool; ProcessLabel string; MountLabel string }

This changes lxc_console template to refers to `.ProcessConfig.Console`

Docker-DCO-1.1-Signed-off-by: Daniel, Dao Quang Minh <dqminh89@gmail.com> (github: dqminh)
Merge pull request #7958 from dqminh/fix-lxc-template-console

fix console attribute in lxc template